I've been wrestling with trying to get dual head working (spanning or individual desktops) on a Dell Optiplex GX260, ATI Radeon 7000/VE vid card, a Dell/Sony 1801FP LCD, and a Dell/Sony 1800FP LCD. I've googled the heck out of this one, but none of the 10-15 useful links (used many mods to XF86Config) got me rolling. I thought somebody out in Fedora-List Land might have the same setup with dual head working - either in spanning or individual desktop mode.
Here's what I used to get my Dell Optiplex GX260 working in xinerama mode:
I have an nVidia GeForce2 MX 100 and the built-in Intel 82845G (Brookdale-G) adapeter.
It's working very well though getting it working required a few tweaks to the XF86Config file after the initial X -xf86config step.
For some reason recent versions of KDE don't use font anti-aliasing in dual-head mode. It used to work just fine, something to do with using hardware anti-aliasing.
You can make it better by not using a font server, and just specifying font paths directly in XF86Config, though it's still not great. I'm using XFCE instead and it's great.